Archive for BepiColombo

BepiColombo goes to Mercury

Posted in The Universe and Stuff with tags , , , on October 24, 2018 by telescoper

You may have missed the news that the joint Japanese-European (JAXA-ESA) Mission BepiColombo was successfully launched on October 19th 2018 and is now on its way to the planet Mercury, where it will arrive in December 2025.

As it happens I’ve just finished delivering a set of lectures on gravitational dynamics, part of which was devoted to orbital mechanics. One of the problems I worked out during these lectures was the Hohmann Transfer Orbit which is the simplest way to get a spacecraft from Earth to, e.g., Mars (which take 8 to 9 months to reach).

Since the radius of Mercury’s orbit is 0.39 AU (compared with Mars’s 1.52 AU) you might think it would take a similar time to reach Mercury, but designing a trajectory that results in a controlled encounter with Mercury in an efficient manner is much harder than for Mars (largely because Mercury is moving much faster). The solution to this problem involves a series of encounters with VEarth, Venus and Mercury each of which results in an adjustment to BepiColombo’s orbit until it finally encounters the target planet at a reasonable speed. This approach takes over seven years, but it saves an enormous amount on fuel – using the gravitational boost from planetary encounters instead of firing rockets.

Here’s a video showing this complex but fascinating example of orbital mechanics in action:

p.s. the dates in the video correspond to the originally planned launch date of 5th October, so are off by a couple of weeks.

Space Anomaly

Posted in Science Politics, The Universe and Stuff with tags , , on December 17, 2009 by telescoper

After yesterday’s marathon, I’m not planning today to post another lengthy item about the STFC prioritisation exercise which is now public. However, a number of people have asked me about an apparent anomaly in the rankings and, despite the hostile reception I received on the e-astronomer when I posted a comment there, I’ve decided to mention it briefly here in an attempt to explain what looks at first sight like a very strange state of affairs.

BepiColombo (no relation) is a Mercury Orbiter mission by the European Space Agency (ESA). It was selected as a result of a lengthy Europe-wide process. The UK space science community showed relatively little interest in the mission, but it had sufficient support elsewhere to avoid being cancelled about three years ago. So it was picked for the programme, and is now scheduled for launch in 2014. It will take about 6 years to reach Mercury and will take data for a year or two after that.

As is the case with these big ESA “cornerstone” missions, participating countries are called upon to bid to build instruments to fly on the spacecraft. Although this requires an additional investment from the funding agencies (in this case STFC) beyond the annual subscription, this is essentially the only way of securing a science return for UK Plc on the ESA subscription. The UK is in fact involved in two instruments on BepiColombo, a magnetometer and an X-ray spectrometer, although it is the second of these that has the main funding commitment from STFC. Roughly speaking, STFC has commissioned UK scientists and given them funds to build a UK part of BepiColumbo.

I’ll remark here that I always thought the most interesting thing about Mercury is its magnetic field – it’s quite surprising even that it has one – so given the chance I’d prefer to have seen the UK getting more involved in that. But what do I know? I’m just a physicist…

Anyway, in the UK’s recent prioritisation exercise, BepiColombo was graded 1 on a scale of 1 (low) to 5 (high), reflecting the relatively low interest in this mission among UK space scientists. Many projects rated 3 were cancelled, and even those rated 4 and 5 are going to have their funds cut by 15 to 20% so it looks very strange to have BepiColombo retained in the final programme, especially if you’re working on an alpha-3 project that’s just been canned.

However, it’s all a bit more complicated than that. While the UK itself wasn’t particularly interested in this mission, it did attract strong support in the rest of Europe. The UK signed up to the whole ESA menu and was thus obliged to go along with it; a la carte was not an option. ESA decides its programme, with UK input, but we do not have a veto. STFC (and previously PPARC) entered into various agreements, including a Memorandum of Understanding, from which it would be disastrous to back out.

I don’t know how much BepiColombo is costing STFC, but it’s likely to run into millions. That money could have supported other things in the astronomy programme, including postdoctoral grants. But before you jump to the conclusion that astronomy has been stitched up, remember that the ESA subscription has also opened up new areas of research through missions such as Planck and Herschel. These are a boon to our research, but the privilege of being allowed to participate in them comes at the price of having to support things the UK astronomy community is less keen on. In this particular example the politics of the situation and the need to fulfil our obligations within ESA have trumped the scientific judgement of the UK community.

To put this another way, would you want to scrap UK participation in this mission if it also meant binning our involvement in Herschel, Planck, JWST and all the rest.

I’m not advocating we scrap BepiColombo any more than we should scrap any of the other primary elements of the ESA programme. However, I do think that the nature of this balancing act should be more widely known. Otherwise, as things stood, it just looks like some vested interest has taken the funds from more deserving causes in order to promote a pet project. I hope I’ve made it clear that did not happen and that STFC had no choice but to fund BepiColombo.

I think it helps to get these things out in the open, in apparent contrast to some colleagues in the space lobby who seem to prefer to silence debate rather than engage with it. It’s no wonder people get suspicious when that’s the attitude shown by those in positions of responsibility on STFC committees.

If I’ve said anything unfair or unreasonable here please feel free to comment, as long as you can refrain from gratuitous abuse…